The present invention relates to a signal processing apparatus and a signal processing method, both designed to convert a first digital broadcast having a prescribed transmission frequency on a first network, to a second digital broadcast signal having a prescribed frequency on a second network.
Cable television companies have been delivering digital broadcast programs from one network to another. For example, they have been receiving the multi-channel broadcast programs via artificial satellites and transmitting the programs to households via the networks.
In this case, the digital broadcast program on the first network cannot be delivered in the second network only if the modulation mode is changed to another by means of a modulator-converter-transimitter or the like. This is because the digital broadcast program has a network information table (NIT) that contains physical data items concerning a transmission path. Further, it is necessary to change the transmission frequency data item and similar data items contained in the NIT of the digital broadcast data, to data items that can be used in the second network.
The NIT contains a program data item, too. A set top box (i.e., household receiver) connected to a cable television transmission path is designed to detect the NIT and receive the program identified by the program data item.
Hence, the NIT of the digital broadcast data delivered in the first network is detected, and the NIT detected is converted so that it may comply with the second network. That is, the NIT of the digital broadcast data delivered in the first network is replaced by an NIT complying with the second network. The digital broadcast data is thereby obtained in the second network.
To deliver a digital program broadcast in a network, in any other network, the contents of the NIT of the digital broadcast data are very important. If the physical data and service data transmitted in a network are not correctly related to those transmitted in another network, digital broadcast programs cannot be delivered appropriately.
Accordingly, an object of this invention is to provide a signal processing apparatus that makes it easy to determine the relation between the physical data and service data transmitted in a first network and the physical data and service data transmitted in a second network.
If the contents of the digital broadcast data transmitted in the first network, such as service data and the number of transport streams to be transmitted, may be changed, the above-mentioned data must be prepared again.
Thus, another object of the invention is to provide a signal processing apparatus and a signal processing method, which can automatically apply changes made in the first network to the second network.
Still another object of this invention is to provide a signal processing apparatus and a signal processing method, which can automatically respond to changes, if any, made in the number of transport streams transmitted from the first network.
Another object of the present invention is to provide a signal processing apparatus and a signal processing method, which can automatically respond to changes, if any, made in the number of service items contained in the digital broadcast data transmitted from the first network.
A signal processing apparatus according to the invention is designed to convert a first digital broadcast having a prescribed transmission frequency on a first network, to a second digital broadcast signal having a prescribed frequency on a second network. The apparatus is characterized by comprising: first frequency-converting means for converting the frequency of the first digital broadcast signal, thereby to generate a first digital modulated signal; demodulating means for demodulating the first digital modulated signal supplied from the first frequency-converting means, thereby to generate digital broadcast data; table-detecting means for detecting a network information table which is physical information about a transmission path, from the digital broadcast data supplied from the demodulating means; table-changing means for changing at least transmission frequency data contained in the network information table detected by the table-detecting means, to data that complies with the second network; table-replacing means for replacing the network information table supplied from the demodulating means, with the network information table supplied from the table-changing means; display means for displaying the contents described in the network information table of the digital broadcast data supplied from the demodulating means and complying with the first network, and also the contents described in the network information table of the digital broadcast data replaced by the table-changing means and complying with the second network; modulating means for modulating the digital broadcast data whose network information table has been replaced by the table-replacing means, thereby to generate a second digital modulated signal; and second frequency-converting means for converting the frequency of the second digital broadcast signal, thereby to generate the second digital broadcast signal.
In the signal processing apparatus according the invention, the display means displays the contents described in the network information table of the digital broadcast data complying with, for example, the first network, along with the contents described in the network information table of the digital broadcast data complying with the second network.
Another signal processing apparatus according to this invention is designed to convert a first digital broadcast having a prescribed transmission frequency on a first network, to a second digital broadcast signal having a prescribed frequency on a second network. This apparatus is characterized by comprising: first frequency-converting means for converting the frequency of the first digital broadcast signal, thereby to generate a first digital modulated signal; demodulating means for demodulating the first digital modulated signal supplied from the first frequency-converting means, thereby to generate digital broadcast data; table-detecting means for detecting a network information table which is physical information about a transmission path, from the digital broadcast data supplied from the demodulating means; analyzing means for analyzing information about the first network, on the basis of the network information table detected by the table-detecting means; comparing means for comparing the information about the first network analyzed by the analyzing means, with the previous information about the first network; table-changing means for changing the network information table of the first network to one that complies with the second network, on the basis of the information about the first network, which has been generated as results of comparison accomplished by the comparing means; table-replacing means for replacing the network information table supplied from the demodulating means, with the network information table supplied from the table-changing means; modulating means for modulating the digital broadcast data whose network information table has been replaced by the table-replacing means, thereby to generate a second digital modulated signal; and second frequency-converting means for converting the frequency of the second digital broadcast signal, thereby to generate the second digital broadcast signal.
A signal processing method according to the present invention is designed to convert a first digital broadcast having a prescribed transmission frequency on a first network, to a second digital broadcast signal having a prescribed frequency on a second network. The method is characterized by comprising: a first frequency-converting step of converting the frequency of the first digital broadcast signal, thereby to generate a first digital modulated signal; a demodulating step of demodulating the first digital modulated signal generated in the first frequency-converting step, thereby to generate digital broadcast data; a table-detecting step of detecting a network information table which is physical information about a transmission path, from the digital broadcast data generated in the demodulating step; analyzing step of analyzing information about the first network, on the basis of the network information table detected in the table-detecting step; comparing step of comparing the information about the first network analyzed by in the analyzing step, with the previous information about the first network; table-changing step of changing the network information table of the first network to one that complies with the second network, on the basis of the information about the first network, which has been generated as results of comparison accomplished in the comparing step; table-replacing step of replacing the network information table generated in the demodulating step, with the network information table generated in the table-changing step; modulating step of modulating the digital broadcast data whose network information table has been replaced in the table-replacing step, thereby to generate a second digital modulated signal; and second frequency-converting step for converting the frequency of the second digital broadcast signal, thereby to generate the second digital broadcast signal.